JPS5918432B2 - mixed phosphor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to mixed phosphors, and more particularly to improved long-afterglow phosphors.

So-called long-afterglow phosphors, in which the phosphor emits light by excitation with electron beams or ultraviolet rays, and the emission gradually decays after the excitation is stopped, are essential for cathode ray tubes for radar, cathode ray tubes for slow scan television image reception, etc. belongs to.

Generally, the afterglow time of a phosphor is longer when excited by ultraviolet light than when excited by electron beam.

Currently known phosphors with long electron beam excitation emission are ZnF2:Mn or (Zn, Mg)F2:
Fluoride-based materials such as Mn, KMgF3:Mn, and MgF2:Mn are known. Some of these phosphors exhibit extremely long afterglow properties, on the order of seconds, until the emission intensity decays to 1/10, but fluoride-based phosphors can be easily irradiated with electron beams. This has the disadvantage of causing burning of the fluorescent surface and deterioration of characteristics, which limits the lifespan and operation at high current densities. Other phosphors with long afterglow after electron beam excitation include Zn2SiO4:Mn and AS, and it is said that the time required for the intensity of the electron beam excitation emission of these phosphors to become 1/10 is 125 msec. In order to achieve a longer afterglow time, a method is known in which two types of phosphors are combined and the emission of light from one phosphor by electron beam excitation excites the other phosphor. The light emission excited by the electron beam attenuates in a few μsec to several tens of μsec, but the light emission of the other phosphor that is simultaneously photoexcited has a long afterglow, and as a result, the electron beam excitation causes a long afterglow emission. is obtained. An example of this is a blue-emitting phosphor of ZnS:AgCl as one fluorophor and a (Zn,Cd)S:
There is one that uses a yellow-emitting Cu phosphor.

When these two types of phosphors are used, during electron beam excitation,
It emits almost white light, but after excitation stops, the blue color quickly attenuates (becomes VIO in 40 to 60 Psec), and a yellow afterglow excited by blue (becomes VIO in 400 msec) is observed. The color of the emitted light changes from white to yellow over time, making it difficult to see the screen. Furthermore, the phosphor that emits light upon blue excitation is Cd of (Zn, Cd)S.
Since a certain amount or more must be added to reduce the energy range so that it can be excited by blue light, it is difficult to obtain a color with a wavelength shorter than yellow, such as a long afterglow of green light emission. Therefore, it has been impossible to construct a color screen using red, green, and blue, which have long afterglow properties. The present invention aims to improve the drawbacks of the conventional long-afterglow phosphors, such as the fact that the emitted light color changes with the passage of time and the fact that a long-afterglow emitted light color cannot be freely obtained. The purpose is to provide a phosphor that can

In order to achieve this object, the present invention uses CaO:Zn, which does not emit visible light upon electron beam excitation but emits light in the ultraviolet region, as one of the phosphors to be combined, and uses one of the above-mentioned phosphors as the other phosphor. ZnS:Cu or (Zn,Cd)S that emits visible light when excited by the ultraviolet light emission of the phosphor:
This uses Cu.

In this way, the range of selection of the other phosphor that emits light with a long afterglow upon excitation of one phosphor is widened, and it becomes possible to use phosphors that emit light of various colors. Furthermore, since the light emitted when excited by an electron beam is ultraviolet rays, it is invisible to the human eye, but the color of the emitted light from the other phosphor excited by this ultraviolet ray becomes visible gradually. The color of the emitted light does not change over time. Examples of phosphors that emit ultraviolet light when excited by electron beams include CaO:Zn, Ca
O:Pb etc. are known, and 330 nm and 3
It shows an emission peak wavelength of 63 nm. On the other hand, the phosphors that exhibit long afterglow fluorescence when excited by the ultraviolet rays mentioned above are:
(Zn, Cd)S:Cu is suitable. In this case, the color of the emitted light can be varied over a wide range by changing the amount of Cd. In order to use these phosphors in cathode ray tubes,
First, a long afterglow phosphor is coated on the screen, and then an ultraviolet-emitting phosphor is coated on top of the screen to form a two-layer structure, thereby allowing efficient conversion from electron beam to ultraviolet to visible light.

Next, examples of the present invention will be described.

Example 1 CaO as a phosphor that emits ultraviolet light upon electron beam excitation:
Zn is used, and ZnS:Cu is used as a phosphor that emits visible light upon excitation with ultraviolet light.

By uniformly coating ZnS:Cu on a cathode ray tube screen and coating CaO:z1 thereon, green long-afterglow light emission was observed by electron beam excitation. Note that similar results were obtained when CaO:Pb was used as a phosphor that emits ultraviolet light upon electron beam excitation. Example 2 Using CaO:Zn as a phosphor that emits ultraviolet light by electron beam excitation,
As a phosphor that emits visible light when excited by ultraviolet light (ZnO
J) CdO. l) s: Use Cu.

When these were applied to a cathode ray tube screen in the same order as in Example 1, yellow long afterglow luminescence was obtained by electron beam excitation. Ca is added to the phosphor that emits ultraviolet light by electron beam excitation.
Similar results were obtained using O:Pb. Example 3 In Example 2, when the phosphor that emits visible light when exposed to ultraviolet rays was changed to (ZnO8CdO2)S:Cu, orange long afterglow light emission was obtained by electron beam excitation.

Claims (1)

[Claims] 1. A first phosphor made of CaO:Zn that does not emit light in the visible region but only in the ultraviolet region by electron beam excitation, and a first phosphor that is excited by the light in the ultraviolet region of the first phosphor. ZnS:Cu or (Z
A mixed phosphor comprising a second phosphor made of n,Cd)S:Cu.